Thin-film semiconductor devices such as thin-film transistors and thin-film diodes are classified into amorphous devices and crystalline devices, depending on the kind of silicon used. Since amorphous silicon is inferior in physical characteristics such as field mobility and conductivity to crystalline silicon, crystalline semiconductor devices are required in order to obtain excellent operating characteristics.
However, to crystallize a silicon film, a high temperature exceeding 600.degree. C. is needed. Also, it takes a long time to crystallize the film. Where crystalline silicon devices are mass-produced in practice, several crystallizing machines are required. Consequently, huge investment in equipment results in increased costs.